Dreissena polymorpha

Identification

Caption

Lampsilis siliquoidea with attached zebra mussels (Dreissena polymorpha), Lake St. Clair, Michigan. The introduction of zebra mussels to North America is one of the great ecological disasters of our time. Their initial entry was from ship ballast emptied into Lake St. Clair, Michigan. They rapidly spread throughout much of the Great Lakes, then into smaller inland lakes, and most recently into the Mississippi River system. The native mussels in Lake St. Clair are not reported to be completely eliminated. The part of the Lampsilis covered in the picture is that part of the animal exposed above the substrate. Like most of our freshwater mussels, Lampsilis stays buried with only enough of the posterior shell exposed to allow the incurrent and excurrent siphons to operate. The Lampsilis shown here is a female, as shown by the posterior bulge in its shell.